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A flexible power control method for grid-connected inverters in unbalanced grid

A control method and power control technology, applied in the direction of output power conversion device, AC power input conversion to DC power output, electrical components, etc., can solve problems such as large amount of calculation, reduction of harmonic content of output current, complex structure, etc. Achieve the effects of improving stability, eliminating negative sequence current, and simple structure

Active Publication Date: 2019-11-15
SOUTH CHINA UNIV OF TECH
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0004] The purpose of the present invention is to solve the disadvantages of complex structure and large amount of calculation of the control strategy of the grid-connected inverter under the unbalanced grid in the prior art, and provide a flexible power control method for the grid-connected inverter under the unbalanced grid. Use a strategy with a simpler structure to achieve flexible power control, that is, it can switch between adjusting active and reactive power fluctuations and eliminating negative-sequence grid current, and can optimize the power according to the control objectives and combine the advantages of the three. control, and can effectively reduce the harmonic content of the output current

Method used

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  • A flexible power control method for grid-connected inverters in unbalanced grid
  • A flexible power control method for grid-connected inverters in unbalanced grid
  • A flexible power control method for grid-connected inverters in unbalanced grid

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Embodiment

[0056] exist figure 1 In , the circuit diagram of the three-level grid-connected inverter is given. The three-level three-phase inverter is connected to the grid through the filter inductor L and the equivalent resistance R.

[0057] Positive and negative sequence components of the grid voltage in the αβ coordinate system (e + α , e + β) and (e - α , e - The calculation formula of β) is:

[0058]

[0059] Among them, e + αβ=e + α+j e + β,e - αβ=e - α+j e - β, eαβ=eα+j eβ, T is the fundamental frequency period of the grid, and the positive sequence and negative sequence components of the grid current in the αβ coordinate system (i + α,i + β) and (i - α,i - β) It can be obtained by the same method only by changing the voltage component in formula (1) into a current component.

[0060] The grid-side voltage complex vector e and current complex vector i can be expressed in the dq coordinate system as:

[0061]

[0062] Among them, e + dq and e - dq represe...

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Abstract

The invention discloses a flexible power control method of a grid-connected inverter under an unbalanced power network. The active and reactive power fluctuations of the grid-connected inverter underthe unbalanced power network are regulated by the flexible power control method. The flexible power control method of grid-connected inverter under unbalanced power network includes the analysis of active power and reactive power frequency doubling component under unbalanced power network, Reasonable active and reactive power reference values are calculated to regulate power fluctuation, and thenthree vectors are selected by model predictive power control, and their duty cycles are adjusted to control the switching devices of three-level inverter. The method of the invention can realize the flexible power control, reduce the active and reactive power fluctuation under the unbalanced power network, and the inverter controlled by the method of the invention has good steady-state performanceand can effectively reduce the harmonic content of the output current.

Description

technical field [0001] The invention relates to the technical field of grid-connected inverter control, in particular to a flexible power control method for a grid-connected inverter under an unbalanced power grid. Background technique [0002] With the increasingly serious environmental problems and energy crisis, the distributed power generation technology using renewable energy such as solar energy and wind energy has received more and more attention. The inverter is the interface between the distributed generation system and the grid, and its control performance will determine the quality of power supply. Due to a series of uncertain factors in the actual power grid, the power grid will be unbalanced. The traditional control strategy that does not consider the unbalanced power grid will reduce the output current quality of the grid-connected inverter and bring negative effects such as power shocks. [0003] The existing control strategies for unbalanced power grids use ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02M7/483H02J3/38
CPCH02J3/38H02M7/483
Inventor 康龙云程建材胡毕华罗璇张健彬王旭
Owner SOUTH CHINA UNIV OF TECH
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